Node.js 22 support

[jbudz]

elastic/kibana#198790

We're looking into upgrading Kibana to Node.js 22 but can't install this package due to

ems-client/package.json

Line 74 in cd38af0

"node": ">=18 <=20"

Would it be possible to add support for v22?

[jsanz]

Thanks for the ping @jbudz, opened #552 to upgrade the library. After merge I'll do a patch release and open the corresponding PR in Kibana for upgrade.